Technical Field of the Disclosure
The present disclosure relates generally to the manufacturing of brushes for cleaning electronic components, and more particularly to a method for producing a cored brush comprising polyvinyl formalin bristles.
Description of the Related Art
A step in the manufacturing process of certain electronic components such as computer hard drive disks and silicon wafers is cleaning the components with specialized brushes. One such type of brush comprises bristles of cured PVA, or polyvinyl formalin. Polyvinyl formalin is a tough sponge-like material which is formed by pouring PVA into a mold and heating it.
In existing systems, the end product after the PVA solution is cured is a brush similar to that shown in prior art FIGS. 1-3 where the bristles are made up of polyvinyl formalin material. FIG. 1 shows a small diameter “Arc Fin” brush, FIG. 2 shows a large diameter “Arc Fin” brush, and FIG. 3 shows a cutaway view of a plastic core that is present in all Arc Fin style brushes such as those depicted in FIGS. 1 and 2. The Arc Fin brushes depicted in FIGS. 1 and 2 are manufactured by casting PVA over the plastic core depicted in FIG. 3 which as shown comprises a plurality of channels that pass through from a first face to an opposite and second face.
During the manufacturing of brushes such as those described above, the core (shown in FIG. 3) is placed in a plastic mold having an interior surface defining a cavity which is a negative shape of the desired final geometry of the product as is well known in the art of molding. An uncured liquid PVA solution is introduced into the cavity where it flows around the core and through the channels of the plastic core. Next, the PVA is cured by elevating its temperature during which the PVA transforms into a white spongy material. With the liquid now solid, the core and the sponge are bound together via mechanical entrapment of the core within the cast sponge. While there is some level of adhesion between the PVA and the plastic, the adhesion is minimal and not sufficient to hold the brush together alone, particularly when the finished device is in use. Instead, the geometry of the hardened components is primarily responsible for maintaining their tight fit to one another, rather than any chemical bonding between the two components.
As shown in FIGS. 1-3, the center point of the brush includes a keyed center hole that provides for a tight fit to a shaft (not shown) to which the brush will be mounted. In use, the final product shaft and brush are submerged in a chemical bath, and then rotated. Finally, the rotating brush is pressed against the surface to be cleaned.
FIGS. 4 and 5 illustrate examples of cylindrical brushes made via the PVA cast process according to the above-mentioned description. FIG. 4 depicts a cylindrical brush having elongated nodules and FIG. 5 depicts a cylindrical brush having round nodules and a cylindrical center hole running longitudinally therethrough. As a component of a cleaning system, the brush may be mounted to a shaft by sliding the shaft (not shown) through the center hole. The shaft and its tight fit provide further rigidity to the brush. The mounting process is typically performed by the end user.
Once the brush is mounted to the shaft, the shaft is rotated thereby causing the brush to rotate where it is used for cleaning hard disk drives, silicon wafers, and other sensitive electronic components during the manufacturing process of those components. Although such systems work reasonably well, there are nevertheless drawbacks and additional improvements of the conventional cleaning brush are needed.
It has been considered to simplify the process by providing a unified core and brush system; that is, a brush pre-mounted on a polymer core. A drawback to the conventional method of manufacturing brushes such as those described above is that the PVA, the primary component in the PVA solution used in the casting of the polyvinyl formalin bristles does not readily adhere to the surface of the plastic core. This weak mechanical unification between the core and the brush provides a great deficiency to such systems. The entire assembly is spun about a center axis running the length of the cylinder and the brushes are pressed against the surface of the object to be cleaned, and the cleaning chemical is applied via physical contact from the brushes. During this process, torque is generated on the brush in the opposite direction of rotation. The presence of this torque can cause the core and the brush to become dislodged from one another. Thus, it is imperative that they be mechanically unified to prevent slippage between the two and to maintain the same rotational velocity in the brush as present in the core.
In some other conventional systems, the weak connection between the plastic core and the PVA solution is not an issue because of the lock and key type assembly of those structures. Further, in those systems and other systems the fact that PVA does not adhere is actually desirable because it facilitates the manufacturing process by allowing the cured PVA to be easily separated from the mold after casting. One conventional method anticipated to alleviate the afore-mentioned problems is to use metal rods and cavities to which the PVA may bind. However, this method fails because the PVA in its liquid state contains highly concentrated sulfuric acid which can cause serious damage to the user.
There is thus a need for a method to produce a brush pre-mounted or integral with a polymer core. Such a needed method would provide strong mechanical bonding between the core and the brush to prevent slippage between them. Further, such a method would allow the PVA to firmly adhere with the plastic core. These and other objectives are accomplished by the present embodiment.